Automatic thread-cutting-machine attachment



March 16 1926. 1,577,206

a. s. DEMPsTER AUTOMATIC THREAD CUTTING MACHINE ATTACHMENT Filed June 6, 1925 E E IH MI i MMM,MKW,KW

Patented Mar. 16, 1926.

UNITED "STATES. PATENT o-sFicE.

GEORGES DEMPSTER, F DETROIT, MICHIGAN, A SSIGNOR TG ROBERTS BRASS'MANU- FAGTU-B/ING- COMPANY, 0F DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

AUTOMATIC THREADCUTTING MAGHINE ATTACHMENT.

Application. filed; June 6,

To all to 710m it m a-j concern Be it known that I, GEORGE S. DEMPSTER, a. citizen of. the United Statesv of America, residing at Detroit, in. the county of Tayne 6 and State of Michigan, have invented certain new and useful. Improvements ii'rAutomati-c. Thread-Guttmg Machme Attach ments, of which the following is. a. specifica ti on, reference. beinghad therein to the accompanying drawings.

This, invention relates to. thread cutting machines and particularly relates... to machines providing for an automatic periodic reversal of the direction. of. drive to the thread. cutting tOOit so as to alternately advance the latter to enter the. work and retract the same- It is the. object of theinvention. to. prevent damage either to the machineor work, in case retractionof the tool failsto take-place at the proper time, by providing an auto.- matic device which will respond to an ab.- normal advance of the tool holder by cutting off the drive to. the endangered elek ments of the machine.

In tl1e. drawin Figure. l isa diagrammatic plan view of the improved. machine Figure'Z is. a view in elevation. of an in.- 30 termittently acting drive mechanism enrpioyed'. at. one end of the machine.

In theseviews 1, 2,. 3 and" 4: designate frame elements and 5 a shaft journaled in the. elements 1 and 3 and carrying a holder 5? for a tap, or. die (not shown). Said shaft is adapted to be driven through gears 6 and 7, from. ash-aft 8, the, latter gear. being relatively long; so. thatv it. may continue in driving engagement with the 'geartiduring the sliding travel of the shaft 5 requisite to operation of thetooli upon the. work and -i.ts.;.withdrawall therefrom. 9 and 1.0 are reversely driven pulleys loosely moun ed upon the. shaft 8 and respectively carrying clutch elements 11 for alternativeengagement by asliding douahle friction clutch member l2psplined upon said shaft and actualile back. and forth by an intermediately pivoted lever 13. Said lever is automatically controlled by a cam. 14 fast upon a shaft 15 and of any suitable construction for shifting the clutch member 12 alternate- Ly into enga ement with. the two clutch members-11.; he shaft 15-is driventhrough a. wor1u16 and worm Wheel. 17. from ashaft 1923.v Serial- No. 643,666.

18 which in turn. is driven through bevel gears 1 9 from a shaft 20; The shaft 20 is adapted to be driven: through gears 21 and I 21 from a shaft 22. carrying the drive pulley 2.3. The gear 21- is loose upon the shaft 20 and is rigidly connected to a clutch member 25 with which is engageahle a clutch member 24: splined, upon said shaft. An intermediately pivoted lever 26 controlsfthe clutch 24, 25,. and in: the normal operation. of the machine maintains said clutch closed, as shown in full: lines in. the drawing. 27 is a rotary workholder carrying a plurality of chucks 2,8 for engaging: the,- work. Through a periodic angular advance of: said work holder; the chucks are adapted to consecutively register their work with the. tool. The periodic drive meansv for the work holder comprises an ordinary Geneva wheel 29,. on the shaft 30. of said work, holder,

and the usual drive element 31. for said wheel, the latter being fast upon the. shaft 32. is. a cam upon the shaft. 15. which acts through a lever 33 to advance and retract the shaft 5 to and from. the position in which the tool initially engages. the work. Thus, normally the cams 1a and 32. and the actuating element 81 are. continuously driven. The clutch member 12. is periodically shifted back and forth tov reverse the drive. tov theshaft 5,,the lever 33- periodically oscillates to effect travel of the tool holder to and from: its. initial position and in. the

intervals when, the tool holder is, retracted,

the work holder undergoes its indexing movement or angular advance.v

The operation of the machine as so far described .is defective in that at times the belt upon. one. of. the drive pulleys 9 and 1 0 may slip or the clutch member '12.. may at times fail to. positively engage one of the clutch members 11, resulting in a failure of the. shaft; 5 to reverse its direction of: rota:- tion and effect withdrawal. of the threading tool when; the latter has engaged the work through the required. distance.

Under such conditions, it is necessary to immediately out off the drive to. the machine and it is particularly essential to prevent the Work holder from undergoing its periodic angular advance, or indexing movement, since such movement, while the tool is engaged wit-lithe work, means usually not only destruction of the work but serious damage to the machine. Thus, a failure of the tool to withdraw from the work frequently results in bending of the spindle 5, when the work-holder indexes, and the owner oi. the Illfltlllllt, is put to a considerable cxnense for repairs, losing the production or the machine in the meantii'nc. The mechanism 32, 32-3 i'ior periodically advancing and retracting the tool holder to and from its initial position is also likely to be damaged in case engagement of the tool in or on the work prevents the worleholder from :t'reely responding to said mechanisi'n.

As a remedy tor such occasional detective operation. the invci'ition provides an automatic device which will respond to an abnormal advance oi the tool-holder toward the work by cutting oil the drive to the work-holder and to the mechanism for reciprocating: the tool holder so that no damage will he done. Thus 34, 35 is a bell crank lever, pivoted at 36 upon the :trame element 1 and having;- its arm 31- projecting into the path oi advance oi? the gear (3. The other arm oil said hell crank carries a latch 37 whereby a tripping: plunger 38 is normally held retracted. In case the tool holder 5, with its shal t 5 and gear 6, ad vances abnormally toward the work, the bell crank 34-, is rocked snllieiently to withdraw the latch 37 from engagement with the ilungrer 3S whcreinmn a coiled spring 35) projects said plunger, throwing the lever 26 to the dash line position of the drawing; and oliiening the clutch ll, Thus. the drive to the cams Lt and 3:

4 and to the Geneva wheel mechanism 20, 231 is cut oil, the indexinn moven'icnt oi the work holder and the oscillation oi? the lever 33 are prevented, and resulting damznre to the machine and work are avoided. Thus, the operator may give his entire attention to supplying the machine with new work and removing the finished pieces, without necessity of watcln ing, at the same time, to see that the threading tool retracts at the proper time.

, It is to be noted that the described automatic control device for the lever 26 does not interfere with ordinary use of said lever for manually stopping and starting the machine.

hat I claim as my invention is:

1. In a. thread cutting; machine, the combination with a recipro atory and rotativc holder for a. thread cutting tool, of means for rotatively driving}; said holder, a rotatable holder or work cngngeable by said tool, means for maintainina the holder stationary when the tool is advanced, and for periodically advancing the work holder rotatively upon disengagement of the tool from the work, a drive connection to said last named means, and means for cutting oil. said drive connection responsive to an abnormal advance oi the tool holder toward the work holder.

.2. In a thread cutting, machine, the combination with a rotative tool holder, and a complementary work holder, one of said elements being rcciprocatory toward the other, of means for rotativcly driving the tool holder, means for pcriodi wally advancin the work holder rotatively, a drive connection to said last named means, and means for cutting oil said drive connection responsive to an abnormal advance of the reciproeatery holder to and the other holder to prevent further advance ol the work holder.

3. In a thread cutting machine, the combination with a reciprocatory and rotative holder for a thread cutting tool, of means tor rotatively driving said holder, a rotatable holder for work engageable by said tool, means -for periodically advancing the work holder rotatively, a drive connection to said means, a clutch controlling said drive connection, a pivotal control element for said clutch, and a member reciprocatory in unison with the tool holder cngageable with said pivotal element through an abnori'nal advance of the tool holder toward the work holder for opening said clutch.

ii. In a thread cutting machine, the combination with a reciprocatory and rotative holder for a thread cutting tool, of means for rotatively driving said holder, a rotatable holder for work engageablc by said tool. means for periodically advancing the work holder rotatively, a drive connection to said means, a clutch controlling said drive conmotion, a pivotal control element for said clutch, and a member reciprocatory in unison with the tool holder engageable with said pivotal element through an abnormal advance of the tool holder toward the work holder for opening said clutch, and means for manually controlling said clutch independently of said pivotal member.

5. In a thread cutting machine, the co1nbination with a rotative holder for a thread cutting tool, of a complementary rotary work holder, one of said holders being reciprocatory to and from the other, means for rotativcly driving said tool holder, means for periodically advancing; the work holder .rotatively, a drive connection to the last named means, a clutch controlling said drive connection, automatic means for opening said clutch responsive to an abnormal ap proach of the reciprocatory holder toward the complementary holder, and independentmcans for manually controlling said clutch.

6. In a thread cutting machine, the combination with a rotative holder for a thread cutting tool, and a complementary work holder, one of said holders being reciprocatory toward the other, of means for rotatively driving the tool holder, means for periodically advancing the work holder rotatively, a drive connection to the last named means, a clutch controlling said drive conill) nection, a lever affording a manual control of said clutch, a spring for shifting said lever to open the clutch, and means normal- 1y restraining said spring from acting upon the latter releasable through an abnormal advance of the reciprocatory holder toward a complementary holder.

7. In a thread cutting machine, the com bination with a reciprocatory and rotative holder for a thread cutting tool, of a complementary work holder, means for rotatively driving the tool holder, means for periodically advancing the Work holder rotatively, a bell crank lever intermediately pivoted, a member reciprocatory in unison with the tool holder engageable with one arm of said lever upon an abnormal advance of the tool holder toward the work holder, the clutch controlling the rotative advance of the work holder, a lever manually actuable to control said clutch, and means for urging said clutch to open position normally restrained by the other arm of said bell crank lever and releasable by the latter upon abnormal advance of the tool holder.

8. In a thread cutting machine, the combination with a holder for a thread cutting tool, and a complementary work holder, one of said holders being reciprocatory toward the other, of means for rotating one of said holders to engage the tool with the work, mechanism for periodically relatively shifting the two holders transversely to the axis of the tool, a drive connection to said mechanism, and means for cutting off said drive connection responsive to a failure of the reciprocatory tool to retract from the other.

i 9. In a thread cutting machine, the combination with a holder for a thread cutting tool, and a complementary work holder, one of said holders being reciprocatory toward the other, of means for rotating one of said holders to engage the tool with the work, mechanism for periodically relatively shifting the two holders transversely to the axis of the tool, a drive connection to said mechanism, and means for cutting off the drive to said mechanism responsive to an abnormal advance of the reciprocatory holder toward the complementary holder.

10. In a thread cutting machine, the combination with a reciprocatory and rotative holder for a thread cutting tool, of means for rotatively driving said holder, a holder for work engageable by said tool, and automatic means for cutting off the drive to the work holder responsive to an abnormal ad vance thereof toward the work holder.

11. In a thread cutting machine, a rotative holder for the tool, means for advancing and withdrawing the tool, a holder for the work, means for holding the work holder immovable when the tool is being advanced, means for rotating the work holder transversely to the tool, and automatic emergency means for preventing operation of the work holder rotating means upon an abnormal advance of the tool.

In testimony whereof I affix my signature.

GEORGE S. DEMPSTER. 

